Please post a pic and a diagram of expression pedal wiring...

[buzzyreed]

Hello. Dear. Forum. I think I isolated the crackle to the expression pedal in my Allen 120C. After taking the expression pedal completely apart and disconnecting it from the organ and wires, I put it back, incorrectly, I can only assume, because now there is no expression function. About 60% of the crackles are gone but now there's an even more distinct line buzz like an un-grounded non-xlr mic cable. Could someone take a snap shot of their expression pedal wiring and post it here so that I can get mine to work again. I will probably just replace the photo resistors in the thing because that is the only explanation I can figure out for why only the flute and pedal divisions crackle. There are two photo resistors and I suspect one is just gone bad. I suspect I don't have the whole thing grounded correctly which accounts for the line buzz.


Help. No. Really. Help.

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P.S. what is the rating on these particular photo resistors? Can I just go to Radio Shack and use the ones they have there?

[Admin]

There are two LDR's, one for each channel. If one is bad, that channel will have no expression. I don't have a wiring diagram, but if you've lost all expression, either the lamp is out or you have a bad ground. The hum indicates the latter.

The LDR's shunt the signal, so one side of the LDR goes to the signal hot and the other to signal ground. When they are dark, their resistance is high and no attenuation takes place.

I truly doubt the LDR's are the source of the crackling, but you can easily find out by lifting the connection on the hot side for each of them.

[buzzyreed]

Yes, I assume now that it's a faulty grounding. How does one fix that? I supposed I miswired the pedal when I put it all back together, but I assumed as long as the black wires were all connected and all the metal parts were connected it would work ok. Could there be something wrong with my main power supply that is causing the crackle??

This really should't be all that complicated to fix, but it's taken two months now and nothing's better.